# check-spelling/check-spelling configuration File | Purpose | Format | Info -|-|-|- [allow.txt](allow.txt) | Add words to the dictionary | one word per line (only letters and `'`s allowed) | [allow](https://github.com/check-spelling/check-spelling/wiki/Configuration#allow) [reject.txt](reject.txt) | Remove words from the dictionary (after allow) | grep pattern matching whole dictionary words | [reject](https://github.com/check-spelling/check-spelling/wiki/Configuration-Examples%3A-reject) [excludes.txt](excludes.txt) | Files to ignore entirely | perl regular expression | [excludes](https://github.com/check-spelling/check-spelling/wiki/Configuration-Examples%3A-excludes) [only.txt](only.txt) | Only check matching files (applied after excludes) | perl regular expression | [only](https://github.com/check-spelling/check-spelling/wiki/Configuration-Examples%3A-only) [patterns.txt](patterns.txt) | Patterns to ignore from checked lines | perl regular expression (order matters, first match wins) | [patterns](https://github.com/check-spelling/check-spelling/wiki/Configuration-Examples%3A-patterns) [line_forbidden.patterns](line_forbidden.patterns) | Patterns to flag in checked lines | perl regular expression (order matters, first match wins) | [patterns](https://github.com/check-spelling/check-spelling/wiki/Configuration-Examples%3A-patterns) [expect.txt](expect.txt) | Expected words that aren't in the dictionary | one word per line (sorted, alphabetically) | [expect](https://github.com/check-spelling/check-spelling/wiki/Configuration#expect) [advice.md](advice.md) | Supplement for GitHub comment when unrecognized words are found | GitHub Markdown | [advice](https://github.com/check-spelling/check-spelling/wiki/Configuration-Examples%3A-advice) Note: you can replace any of these files with a directory by the same name (minus the suffix) and then include multiple files inside that directory (with that suffix) to merge multiple files together.